The present invention is related generally to the field of machine tools, and more particularly to rotary cylinder assemblies for machine tools.
Machine tools use rotary cylinder assemblies to direct pressurized fluid into a cylinder body that houses a piston for extending or retracting a work piece, and also to direct the pressurized fluid to actuate a chuck that grips the work piece. Many machine tools operate under high fluid pressure environments and rotate the work piece at several thousand revolutions per minute. The high fluid pressure and speeds raise safety concerns. For example, if fluid pressure supplied to the rotary cylinder assembly were suddenly lost, the rotary cylinder could lose its ability to maintain axial force. Thus, the work piece chuck could lose its gripping capability, causing the work piece to be thrown off the chuck and potentially injuring persons nearby.
In order to address these safety concerns, prior art fluid systems for machine tools have incorporated check valve systems into their components to allow trapping or isolation of fluid pressure in the cylinder body and machine tool chuck in the event of loss of fluid pressure. However, prior art check valve systems have some structural and functional disadvantages. For example, the required size of the components and complex configurations employed to accommodate flow passages to the check valve system can make fabrication and assembly costly. It is further believed check valve systems have not been employed with a cylinder body having a piston chamber bore diameter at least as small as three inches. The use of large pneumatic and/or hydraulic components in light duty machine tool applications reduces the useful life of these components for use in medium and heavy duty applications, and also increases fabrication costs.
Therefore, there remains a need for an improved rotary cylinder assembly that employs a lock check system to control fluid flow and pressure for operation of a machine tool work piece. The improved rotary cylinder assembly should be able to employ small components for light duty machine tool requirements while providing the safety of the check valve system in the event of fluid pressure loss. The improved rotary cylinder assembly should also reduce the complexity of fabrication required of the rotary cylinder components needed to house the check valve system. The present invention is directed to provide an improved rotary cylinder assembly that meets these needs, among others.
The present invention is directed to a rotary cylinder assembly for a machine tool that includes a shaft end cover having lock check system that maintains fluid pressure in the cylinder body in the event fluid supply pressure is lost or disrupted. As used herein, the term fluid is intended to encompass any media used in machine tool operation. Aspects of the invention may also have application outside the field of machine tools.
According to one aspect of the invention, there is provided a rotary cylinder assembly that includes a fluid shaft housing coupled to a shaft end cover that houses a lock check system. A cylinder body having an internal bore diameter at least as small as three inches can be coupled to the other side of the shaft end cover. The cylinder body has a piston in the bore that extends and retracts a work piece in response to fluid pressure from a pressurized fluid source selectively supplied to extend and retract ports on the fluid shaft housing. The lock check system includes a pair of check valves, each of which can be selectively piloted open to allow fluid from the other lock check to reverse flow therethrough, thus moving the piston between its extend and retract positions. When fluid supply pressure is lost, the check valve piloted open closes, and the check valve isolates the pressurized fluid in the cylinder body, preventing further extension and retraction of the work piece and locking the work piece to the work piece chuck until fluid supply pressure is restored.
In another aspect of the invention, a rotary cylinder assembly is provided that uses fluid pressure in a cylinder body that houses a piston to extend and retract a work piece in accordance with pressure supplied from one of a retract port or an extend port in a fluid shaft housing. The rotary cylinder assembly includes a lock check system between the fluid shaft housing and the cylinder body that maintains the fluid pressure in the cylinder body to prevent work piece extension or retraction in the event of pressure loss to the extend and retract ports.
In a preferred form, the lock check system includes a pair of lock check cartridges that are housed in a shaft end cover. The lock check system further includes a number of flow paths that extend through the shaft end cover and between the cartridges. In a further preferred form, the number of flow paths of the lock check system includes a first flow path that extends between the pilot port of the first lock check cartridge and the inlet port of the second lock check cartridge, and a second flow path that extends between the pilot port of the second lock check cartridge and the inlet port of the first lock check cartridge. At least a portion of each of the first and second flow paths is formed by a channel in the end face of the shaft end cover. Preferably, the channel is surrounded by a seal that sealingly contacts the fluid shaft housing when the shaft end cover is coupled thereto. In another preferred form, each channel has an offset at the mid-portion of its length.
According to another aspect of the present invention, there is provided a shaft end cover that houses a lock check system. The lock check system includes a pair of lock check cartridges that are housed in a shaft end cover and a number of flow paths in the shaft end cover that interconnect the lock check cartridges and provide fluid flow through the shaft end cover. The number of flow paths of the lock check system include a first flow path that extends between the pilot port of the first lock check cartridge and the inlet port of the second lock check cartridge, and a second flow path that extend between the pilot port of the second lock check cartridge and the inlet port of the first lock check cartridge. At least a portion of each of the first and second flow paths is formed by a channel in the end face of the shaft end cover. Outlet channels can also be provided in the end face of the shaft end cover that extend between an outlet of each lock check cartridge and an adjacent extend or retract through port that extends through the shaft end cover.
Other forms, features, aspect, embodiments, and advantage of the present invention will be apparent in the following description of the preferred embodiment.